Keratin 17 Impacts Global Gene Expression and Controls G2/M Cell Cycle Transition in Ionizing Radiation-Induced Skin Damage.

Keratin 17 (K17) is a cytoskeletal protein that is part of the intermediate filaments in epidermal keratinocytes. In K17-/- mice, ionizing radiation induced more severe hair follicle damage, whereas the epidermal inflammatory response was attenuated compared with that in wild-type mice. Both p53 and K17 have a major impact on global gene expression because over 70% of the differentially expressed genes in the skin of wild-type mice showed no expression change in p53-/- or K17-/- skin after ionizing radiation. K17 does not interfere with the dynamics of p53 activation; rather, global p53 binding in the genome is altered in K17-/- mice. The absence of K17 leads to aberrant cell cycle progression and mitotic catastrophe in epidermal keratinocytes, which is due to nuclear retention, thus reducing the degradation of B-Myb, a key regulator of the G2/M cell cycle transition. These results expand our understanding of the role of K17 in regulating global gene expression and ionizing radiation-induced skin damage.

Gut microbiota accelerates cisplatin-induced acute liver injury associated with robust inflammation and oxidative stress in mice.

BACKGROUND: Gut microbiota has been reported to be disrupted by cisplatin, as well as to modulate chemotherapy toxicity. However, the precise role of intestinal microbiota in the pathogenesis of cisplatin hepatotoxicity remains unknown. METHODS: We compared the composition and function of gut microbiota between mice treated with and without cisplatin using 16S rRNA gene sequencing and via metabolomic analysis. For understanding the causative relationship between gut dysbiosis and cisplatin hepatotoxicity, antibiotics were administered to deplete gut microbiota and faecal microbiota transplantation (FMT) was performed before cisplatin treatment. RESULTS: 16S rRNA gene sequencing and metabolomic analysis showed that cisplatin administration caused gut microbiota dysbiosis in mice. Gut microbiota ablation by antibiotic exposure protected against the hepatotoxicity induced by cisplatin. Interestingly, mice treated with antibiotics dampened the mitogen-activated protein kinase pathway activation and promoted nuclear factor erythroid 2-related factor 2 nuclear translocation, resulting in decreased levels of both inflammation and oxidative stress in the liver. FMT also confirmed the role of microbiota in individual susceptibility to cisplatin-induced hepatotoxicity. CONCLUSIONS: This study elucidated the mechanism by which gut microbiota mediates cisplatin hepatotoxicity through enhanced inflammatory response and oxidative stress. This knowledge may help develop novel therapeutic approaches that involve targeting the composition and metabolites of microbiota.

Ionizing radiation, but not ultraviolet radiation, induces mitotic catastrophe in mouse epidermal keratinocytes with aberrant cell cycle checkpoints.

Ultraviolet radiation (UVR) and ionizing radiation (IR) are common genotoxic stresses that damage human skin, although the specific damages to the genomic DNA are different. Here, we show that in the mouse glabrous skin, both UVR and IR induce DNA damage, cell cycle arrest, and condensed cell nuclei. However, only IR induces mitotic catastrophe (MC) in the epidermis. This is because UVR induces a complete blockage of pRB phosphorylation and cell cycle arrest in the G1 phase, whereas pRB phosphorylation remains positive in a significant portion of the epidermal keratinocytes following IR exposure. Furthermore, Cyclin B1 expression is significantly downregulated only by IR but not UVR. Finally, there are more MC cells in the epidermis of p53-/- mice after IR exposure as compared to wild-type mice. Our results suggest that although both IR and UVR are genotoxic, they show distinct impacts on the cell cycle machinery and thus damage the epidermal keratinocytes via different mechanisms.